Diagnostic ultrasound apparatus provides a comprehensive evaluation of body health and disease. The proven safety and efficacy of ultrasound techniques have resulted in widespread acceptance by both patients and physicians.
Diagnostic ultrasound equipment generates images of structures within the body by transmitting ultrahigh frequency sound waves (typically on the order of 3.0 MHz) and then analyzing the waves reflected from the body structure. Perhaps the most widely used ultrasonic diagnostic apparatus displays structural information of an organ in the form of a two-dimensional image of a selected cross-section of the organ. The ultrasound is typically swept across the organ in the form of a sector scan. The sector scan is ordinarily performed in real time so that the image is available during the examination. In such cases, motion of the organ produces a corresonding moving image.
In cardiology, most diseases are accompanied by both anatomical and blood flow abnormalities. Although two-dimensional anatomical images have proved very useful in detecting, for example, mitral stenosis, intra-cardiac shunts and wall-motion abnormalities, it has been less useful in evaluating aortic stenosis, mitral and aortic insufficiency and congenital defects. In these latter areas, the anatomical defects are extremely small, and often beyond the resolution of conventional anatomical ultrasonic apparatus. However, flow abnormalities created by these defects are much more significant. Thus, if blood flow can be monitored, these abnormalities can be more easily detected.
Some presently-available ultrasound systems provide blood flow information utilizing the Doppler principle. Exemplary Doppler ultrasound apparatus are disclosed in U.S. Pat. No. 4,318,413 to Iinuma et al. and U.S. Pat. No. 4,324,258 to Heubscher et al. A beam of ultrasonic energy is directed toward a blood vessel or other organ in which blood flow information is desired. The moving blood cells reflect the ultrasound energy and either impart an increase or decrease in frequency to the reflected energy, depending on the direction of blood flow, in accordance with the Doppler principle. The magnitude of the frequency shift and direction of shift are detected so that the velocity and direction of blood flow may be ascertained. Such Doppler ultrasound apparatus also typically provide anatomical information using conventional diagnostic ultrasound techniques.
The Doppler ultrasound equipment now in use is deficient in many respects. Perhaps the most serious deficiency is that such equipment is capable of providing blood flow information at only one point or at several individual points in an organ. Since blood flow is frequently not uniform within an organ, even within a relatively small volume, it is difficult to obtain complete blood flow information using such equipment.
The present invention overcomes the above-noted limitations of Doppler ultrasound equipment. The disclosed ultrasonic diagnostic apparatus provides a real-time, two-dimensional blood flow image superimposed on a real-time, two-dimensional anatomical image. Blood flow information is displayed over the entire cross-section or a substantial portion of the cross-section of the organ rather than at a single point or multiple points. Thus, the examiner is able to ascertain blood flow information over an entire organ cross-section or a portion thereof at essentially a single point in time. This and other advantages of the present invention will become apparent to persons having ordinary skill in the art upon reading the following Best Mode for Carrying Out the Invention together with the drawings.